calidation

Red hot validation for React 🌶

yarn add calidation

What's this?

This is a validation library for React! It provides you with powerful and flexible validation, which is probably what you're looking for.

I have written the best blog post of all time about this.

How do you even?

Let's say you have a form you want to validate. Remove that old school <form /> tag and replace it with a fly af <FormValidation /> component!

Step 1: Specify your fields

First, you specify a config object that specifies the names of the fields you want to validate, and the validators to apply to each field.

const formConfig = {
    username: {
        isRequired: 'Username is required!',
    },
    password: {
        isRequired: 'Password is also required!',
        isMinLength: {
            message: 'Password must at least be 8 characters long',
            length: 8,
        },
    },
};

In this config, we validate two fields - username and password. These keys are matched with your <input name /> property. Each matching object is a list of validators.

Here, the key is the name of the validator, and the value is either the error message as a string, or an object with a simple validation configuration. You can add as many validators as you want, and they'll be run from top to bottom. For more about validators, go to the validators section!

Validate that form

Alright, so this is how it looks:

import { FormValidation } from 'calidation';

const config = {...}; // See above
const MyForm = props => (
    <FormValidation onSubmit={props.onSubmit} config={config}>
        {({ errors, fields, submitted }) => (
            <>
                <label>
                    Username: <input name="username" value={fields.username} />
                    {submitted && errors.username && <span>{errors.username}</span>}
                </label>
                <label>
                    Password: <input name="password" value={fields.password} />
                    {submitted && errors.password && <span>{errors.password}</span>}
                </label>
                <button>Log in</button>
            </>
        )}
    </FormValidation>
);

The <FormValidation /> component accepts a function as a child, which is called with an options object containing field values, errors and so on.

The <FormValidation /> component renders a <form /> tag, so you get a nicer user experience out of the box! You can pass an onSubmit event handler, which will be called with the field values and errors:

onSubmit = ({ fields, isValid }) => {
    if (isValid) {
        server.saveAllTheData(fields);
    }
};

Validate complex forms

Some times, you end up with advanced forms, and you don't want to specify all the fields in the same configuration object. There might be many reasons for this, like when certain parts of your form is visible only if certain conditions are met.

For those cases, we have two new components - <Form /> and <Validation />.

The <Form /> component works as the <form /> HTML tag, wrapping the entire complex form. You can put this at the top level of your page container component, for example. This component accepts an onSubmit handler, similar to what you're used to from <FormValidation />.

The <Validation /> component is a descendant of a given <Form /> component, and wraps your input fields, dropdowns and radio buttons. It expects a config prop, an optional initialFields prop, and a function as a child, just like <FormValidation />. Here

Here's an example:

import { Form, Validation } from 'calidation';
const MyPage = props => (
    <Form onSubmit={props.onSubmit}>
        <Validation config={props.config}>
            {({ fields }) => (
                <>
                    Who is your daddy?
                    <input name="daddy" value={fields.daddy} />
                </>
            )}
        </Validation>
        {/* ...tons of other components and other stuff */}
        <Validation config={props.anotherConfig}>
            {({ fields }) => (
                <>
                    What does he do?
                    <input name="dadWork" value={fields.dadWork} />
                </>
            )}
        </Validation>
    </Form>
);

The onSubmit handler will receive a merged object of all the validated fields below it, as well as a merged object of all the errors:

const onSubmit = ({ fields, errors, isValid }) => {
    // fields and errors now contain both `daddy` and `dadWork`
    // isValid is true if all forms are valid, otherwise false.
};

Validators

All validators require a configuration object that looks like this:

someField: {
    isRequired: {
        message: 'This is the error message shown if the validation fails',
    },
},

If you only specify the message key, you can just pass the message string directly, like this:

someField: {
    isRequired: 'This is the error message shown if the validation fails',
},

You can skip validation of a certain validator if you specify a validateIf function. It will receive the other validated fields as an argument.

someField: {
    isRequired: {
        message: 'You need to answer this question',
        validateIf: ({ fields }) => fields.someOtherField === 'foo',
    },
},

If you only want to display errors when the field has been edited, you can use the isDirty flag.

someField: {
    isMinLength: {
        length: 5,
        message: 'Must be minimum of 5 characters',
        validateIf: ({ isDirty }) => isDirty,
    },
},

If you want to do cross validation, or just need access to the other field inputs and / or errors, each validator also accepts a function that receives all fields and the current error state.

password: {
    isRequired: 'You need a password',
},
repeatPassword: {
    isRequired: 'Please fill out the password a second time',
    isEqual: ({ fields }) => ({
        message: 'The two password must match',
        value: fields.password,
        validateIf: fields.password.length > 0, // this can be a boolean too!
    }),
}

Finally, please note that validation happens from top to bottom. The validation will quit once it encounters an error, so you can have multiple levels of validators if you so please.

Default validators

calidation comes with a lot of validators built in. These should be enough for most common use-cases. You'll find them all in the sister package calidators.

isRequired

Validates that a field has some content.

someField: {
    isRequired: 'This field is required', // shorthand
    isRequired: { message: 'This field is required' },
},

isNumber

Validates that a field only contains numeric characters

someField: {
    isNumber: 'You need to enter a number', // shorthand
    isNumber: { message: 'You need to enter a number' },
},

isEqual

Validates that a field equals a given value. The value is cast to a String, and then checked for equality with the === operator.

someField: {
    isEqual: {
        message: 'You need to enter "yes"',
        value: 'yes',
    },
},

isGreaterThan / isLessThan

Validates that a field is greater or less than a given number.

someField: {
    isGreaterThan: {
        message: 'You need to be at least 18 years old',
        value: 17,
    },
    isLessThan: {
        message: 'You can\'t be older than 70 years old',
        value: 66,
    },
},

isEmail

Validates that a field is a potentially valid email address.

someField: {
    isEmail: 'Please enter a valid e-mail address', // Shorthand
    isEmail: { message: 'Please enter a valid e-mail address' },
},

isRegexMatch

Validates that a field matches a given regular expression.

someField: {
    isRegexMatch: {
        message: 'You need to enter four digits',
        regex: /^\d{4}$/,
    },
},

isWhitelisted

Validates that a field is present in a provided whitelist. The whitelist must be an array.

firstName: {
    isWhitelisted : {
        message: 'Bros only, bro',
        whitelist: ['Chad', 'Bret'],
    },
},

isBlacklisted

Validates that a field is not present in a provided blacklist. The blacklist must be an array.

firstName: {
    isBlacklisted : {
        message: 'Bros are not welcome',
        blacklist: ['Chad', 'Bret'],
    },
},

isMinLength

Validates that a field is at least a given number of characters long.

someField: {
    isMinLength: {
        message: 'You need at least four characters',
        length: 4,
    },
},

isMaxLength

Validates that a field is at most a given number of characters long.

someField: {
    isMaxLength: {
        message: 'You can at most have four characters',
        length: 4,
    },
},

isExactLength

Validates that a field is exactly a given number of characters long.

someField: {
    isExactLength: {
        message: 'Norwegian postal codes are four digits long',
        length: 4,
    },
},

Custom validators

You can add your own too! In that case, wrap your app with the <ValidatorsProvider /> component, and pass it an object with your custom validators. It can look like this:

import { ValidatorsProvider } from 'calidation';
const extraValidators = {
    isEven: (config, { errors, fields, isDirty }) => value =>
        Numb